1. Technical Field
This invention relates generally to an apparatus for enabling the keypad of an electronic instrument such as a cellular telephone, and more particularly to such an apparatus which enables operation of the keypad in response to extension of an antenna.
2. History of Related Art
It is very easy to inadvertently depress the keypad of an electronic instrument, such as a cellular telephone, while carrying the phone in a pocket or purse. This is particularly true with today's small cellular telephones. The inadvertent activation of the telephone can lead to a number of problems, ranging from low battery life due to excessive current drain to missing calls because the phone was accidentally turned off.
Heretofore, the only solution to inadvertent activation of the keypad has been to incorporate a "flip" cover over the keypad in order to protect the keys when the phone is carried in a purse, briefcase or pocket. However, flip covers present a number of problems. The three most troublesome problems include the additional steps required to answer a telephone equipped with a flip cover, increased thickness that a flip cover adds to the instrument, and the extra cost added to the instrument as a result of the cover and other added components. More specifically, when a telephone is equipped with a flip cover, the telephone must be removed from a pocket or other place of storage, the flip cover must be opened, the antenna extended, and the "SEND" key depressed to answer the call unless the flip cover is equipped with a switch which automatically answers the call when the cover is opened. The increased thickness added to the instrument as a result of the flip cover decreases the comfort and compactness of the instrument when carried in a pocket. The extra cost added to the manufacture of an instrument equipped with a flip cover does not result in any additional utility of the instrument.
One attempt to reduce the inadvertent activation of the keypad is described in U.S. Pat. No. 4,845,772 issued Jul. 4, 1989 to Metroka et al. In the Metroka radiotelephone, the flip cover activates a hook switch which establishes power to the phone when moved to an open position. While this arrangement is somewhat beneficial, use of the phone to receive or transmit calls still requires extension of the antenna. Furthermore, if the antenna is not extended to its full length, not only is signal reception and transmission quality diminished, but also the antenna will be in undesirably close proximity to the user's head, thereby increasing the user's specific absorption rate (SAR) of electromagnetic energy emitted from the antenna.
It is therefore desirable to have a method of preventing inadvertent activation of a keypad of an instrument without adding steps required to answer a call. It is further desirable to have such an instrument that enables the user to answer a call simply by removing the phone from the user's pocket or other place of temporary storage and fully extending the antenna to its intended operational position. When the antenna is at it's correct operational position, the user can directly respond to the incoming call with assurance that the antenna is at its properly spaced from the user's head and that the signal will not break up due to insufficient antenna length. Furthermore, on outgoing calls it is desirable to have an instrument with a keypad that is enabled simply by extending the antenna of the instrument. It is still further desirable to have such an instrument that has a thin profile and can be comfortably carried in the pocket of a jacket or shirt. It is further desirable to have such an instrument that is economical to produce and does not add significant complexity or cost to the instrument.